Bandwidth Management Through Rate Limiting
Traffic policing allows you to control the maximum rate of traffic transmitted or received on an interface. Traffic policing
is often configured on interfaces at the edge of a network to limit traffic into or out of the network. In most Traffic Policing
configurations, traffic that falls within the rate parameters is transmitted, whereas traffic that exceeds the parameters
is dropped or transmitted with a different priority.
Packet marking allows you to partition your network into multiple priority levels or classes of service (CoS). A packet is
marked and these markings can be used to identify and classify traffic for downstream devices. In some cases, such as ATM
Cell Loss Priority (CLP) marking or Frame Relay Discard Eligibility (DE) marking, the marking is used to classify traffic.
Use traffic policing to set the IP precedence or DSCP values for packets entering the network. Networking devices within
your network can then use the adjusted IP precedence values to determine how the traffic should be treated. For example, the
Weighted Random Early Detection (WRED) feature uses the IP precedence values to determine the probability that a packet will
Use traffic policing to assign packets to a QoS group. The router uses the QoS group to determine how to prioritize packets
within the router.
Traffic can be marked without using the Traffic Policing feature. If you want to mark traffic but do not want to use Traffic
Policing, see the "Marking Network Traffic" module.
Packet Prioritization for Frame Relay Frames
The Traffic Policing feature allows users to mark the Frame Relay DE bit of the Frame Relay frame. The Frame Relay DE bit
is one bit and, therefore, can be set to either 0 or 1. In congested environments, frames with the DE bit set to 1 are discarded
before frames with the DE bit set to 0.
Packet Prioritization for ATM Cells
The Traffic Policing feature allows users to mark the ATM CLP bit in ATM cells. The ATM CLP bit is used to prioritize packets
in ATM networks. The ATM CLP bit is one bit and, therefore, can be set to either 0 or 1. In congested environments, cells
with the ATM CLP bit set to 1 are discarded before cells with the ATM CLP bit set to 0.